"Relative to free cash flow, this item tracked substantially better, at -$0.3 bn vs. JPM -$0.9 bn and was much improved sequentially. … We want to temper enthusiasm by highlighting that a significant driver of the sequentially improved cash generation was a one-time draw-down of finished goods inventory that is likely to prove unsustainable in nature," analyst Ryan Brinkman wrote in a note to clients Thursday. "The outlook was positive in that it called for positive operating income "at some point in 2018," although we believe free cash generation is quite a bit further out."

"Investors will rightly question the quality and repeatability of the FCF development, with the improvements in inventory not repeatable, uncertainty around the sustainability of increasing customer deposits and benefits from ZEV [Zero Emission Vehicle] credits," analyst George Galliers wrote in a note to clients Thursday.

One analyst believes Tesla will have to raise more funding. The company had $3.4 billion in cash at the end of the December quarter.

UBS reaffirmed its sell rating for Tesla shares and its $195 price target.

"Q4 cash burn moderation likely temporary," analyst Colin Langan wrote in a note to clients Wednesday. "While management was confident another capital raise would not be necessary, we remain cautious as we expect cash burn to return to ~$1bn in Q1"18."

Langan predicts given the "limited" profitability of the Model 3 and Tesla"s need to invest more money for the Model Y development, the company will need to raise additional capital from investors.

The company did not immediately respond to a request for comment.

Tesla shares outperformed the market over the previous 12 months, up 32 percent through Wednesday compared with the S&P 500"s 17 percent return.